U.  S   DEPARTMENT  OF  AGRICULTURE, 

DIVISION    OF    ENTOMOLOGY— BUI. LEI  IN    NO.    32,    NEW    SERIES. 

L.  O.   HOWARD,   Entomologist. 


INSECT  ENEMIES  OF  THE  PINE  IN  THE  BLACK 
HILLS  FOREST  RESERVE. 


AX  ACCOUNT  OF  RESULTS  OF  SPECIAL  INVESTIGATIONS,  AV1TH 
RECOMMENDATIONS  FOR  PREVENTING  LOSSES. 


PREPARED  UNDER  THE  DIRECTION  OF  THE  ENTOMOLOGIST, 


By  A.  D.   HOPKINS,  Ph.  D., 

Vice-Direcior  and  Entomologist  of the  West  Virginia  Agricultural 
Experiment  Station. 


WASHINGTON: 
government   printing   office. 

Iim.v;. 


DIVISION  OF  ENTOMOLOGY. 

Entomotog?i&:  L.  O.  Howard. 

First  Assistant  Entomologist:  C.  L.  Marlatt. 

Assistant  Ent&mologiks;  Th.  Pergande,  F.  H.  Chittenden,  Nathan  Banks. 
Investigators:  E.  A.  Sehwarz,  1).  W.  Coquillett,  W.  D.  Hunter,  G.  B;  Simpson. 
Apiarian:  Frank  Benton.  - 

AssMmfe:  R.  B.  Clifton,  F.  C.  Pratt,  Aug.  Busck,  Otto  Heidemann,  A.  N.  Caudell, 

J.  Kotinsky. 
Artist:  Miss  L.  Sullivan. 


i 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

DIVISION    OF    ENTOMOLOGY— BULLETIN    NO.    52,    NEW    SERIES. 

L.  O.    HOWARD,    Entomologist. 


[SECT  ENEMIES  OF  THE  PINE  IN  THE  BLACK 
HILLS  FOREST  RESERVE. 


AN  ACCOUNT  OF  RESULTS  OF  SPECIAL  INVESTIGATIONS,  WITH 
RECOMMENDATIONS  FOR  PREVENTING  LOSSES. 


PREPARED  UNDER  THE  DIRECTION  OF  THE  ENTOMOLOGIST. 


By  A.   D.   HOPKINS,   Ph.  D., 

Vice-Director  and  Entomologist  of  the  West  Virginia  Agricultural 
Experiment  Station. 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE, 

11)02. 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture. 

Division  of  Entomology, 
Washington,  I).  C.  January  22,  1002. 
Sir:  In  the  temporary  absence  of  Dr.  L.  O.  Howard,  Chief  of  the 
Division  of  Entomology,  I  have  the  honor  to  transmit  herewith  the 
manuscript  of  a  paper  entitled  "Insect  Enemies  of  the  Pine  in  the  Black 
Hills  Forest  Reserve,"  Irv  Dr.  A.  D.  Hopkins.  Entomologist  of  the 
West  Virginia  Agricultural  Experiment  Station.  The  extensive  losses 
occasioned  in  recent  years  by  insects  to  forest  lands  in  various  portions 
of  the  United  States,  and  particularly  in  the  North  and  Northwestern 
regions,  have  attracted  great  attention,  and  have  necessitated  investi- 
gations as  to  the  character  of  the  injury  in  order  that  the  most  appro- 
priate methods  of  control  may  be  advised.  The  present  contribution 
is  the  third  of  a  series  bearing  upon  the  insect  enemies  of  coniferous 
trees,  and  comprises  a  summarized  account  of  results  of  a  special 
investigation  that  was  made  during  the  year  1901  under  instructions 
from  this  Division  and  with  the  cooperation  of  Mr,  Clifford  Pinchot, 
Forester  of  this  Department,  together  with  a  consideration  of  valuable 
suggestions  for  preventing  losses,  based  upon  studies  by  Dr.  Hopkins 
extending  over  a  number  of  years.  I  recommend  its  early  publication 
as  Bulletin  No.  32,  new  series,  of  this  Division. 
Respectfully. 


Hon.  James   Wilson. 

St  crt  tary  of  Agriculture. 


H.  Chittenden, 
Acting  Entomologist. 


CONTENTS. 


Page. 

Request,  authorization,  and  instructions 7 

The  investigating  trip 7 

The  conditions  observed 7 

The  amount  of  dead  timber 7 

Historical  references 7 

The  trouble  caused  by  insects 9 

The  primary  enemy 9 

Name  of  the  beetle 9 

Secondary  enemies 10 

The  Oregon  Tomicus  (  Tomicus  oregoni  Eichh. ) 10 

The  coarse-writing  bark-beetle  ( Tomicus  calligraphus  Germ. ) 11 

The  wood-engraving  Tomicus   (Tomicus  cselatus  Eichh.   var.   scopuhrum, 

n.  var. ) 12 

The  dark-red  turpentine  beetle  {Dendrocton  us  miens  Lee.) 12 

The  western  pine  Hylurgops  (Hyhirgops  subcostulatus  Mann. ) 13 

The  pine-root  bark-beetle  (Hylastes  porosus  Er.) 13 

Branch  and  twig  beetles 14 

Ambrosia  or  timber  beetles  and  wood-boring  grubs 14 

Small  trees  dying  from  other  causes 14 

The  rock  pine  pitch-worm 14 

The  pine  weevil 14 

Insect  enemies  of  the  foliage 15 

Natural  enemies  of  the  destructive  and  injurious  insects 15 

Predaceous  enemies 15 

The  1  )luish-green  predaceous  beetle 15 

Clerid  beetles  and  their  larvae 15 

Red-bug  enemy  of  the  bark-beetle  ( Trogosito  virescens  Fab. ) 16 

Other  predaceous  beetles 16 

•  Parasitic  insects 16 

Parasitic  fungi 16 

Birds  as  enemies  of  the  destructive  beetle 16 

How  the  trees  are  attacked  and  killed 17 

Characteristic  features  of  the  living,  dying,  and  dead  trees  infested  and  killed 

by  the  beetle 19 

Borings  and  pitch  tubes 19 

Appearance  of  the  leaves 19 

A  ppearance  of  the  trees  that  have  been  dead  three  years  or  more 19 

Evidence  of  the  work  of  the  beetle  on  old  dead  trees 20 

The  relation  of  wood-boring  insects  and  wood-destroying  fungi  to  the  rapid 

deterioration  of  the  wood 20 


4  CONTENTS. 

gtions  for  preventing  Losses 20 

Methods  of  combating  the  enemy  and  preventing  losses  from  its  ravages. 

To  reduce  the  numbers 21 

Suggestions  for  preventing  further  trouble 22 

To  prevent  losses  from  wood-boring  insects 22 

Th<  protection  of  living  timber 22 

Evidences  of  unnecessary  cutting  of  living  timber 23 

Suggestions  concerning  timber-cutting  contracts 23 

Need  of  further  investigation 24 

Cutting  and  barking  the  infested  trees  in  winter 24 

The  experiments  of  girdling,  cutting,  and  treating  trees 24 


ILLUSTRATIONS 


PLATES. 

Page. 

Plate  I.  Work  of  the  pine-destroying  beetle  of  the  Black  Hills 8 

II.  Work  of  the  coarse-writing  bark  beetle 8 

III.  Work  of  the  pine-destroying  beetle  of  the  Black  Hills.     Fig.  1. — 

Primary  galleries  and  larval  mines  in  inner  bark.     Fig.  2. — Marks 

of  primary  galleries  on  surface  of  scoring  chip 12 

IV.  Work  of  the  pine-destroying  beetle  of  the  Black  Hills.     Fig.  1. — 

A,  Primary  galleries,  larval  mines,  pupa  cases,  and  exit  holes; 

B,  Primary  galleries  grooved  in  surface  of  wood  in  chip  cut  from 
railroad  tie.  Fig.  2. — Evidence  of  cutting  living  trees.  A,  Scor- 
ing chip  from  railroad  tie,  showing  surface  of  wood  not  marked 

by  insects;  B,  Showing  inner  surface  of  bark  from  same  chip 12 

V.  Work  of  the  Oregon  Tomicus.  Fig.  1. — A,  Galleries  engraved  in 
surface  of  wood  cut  from  old  dead  tree;  B,  Bark  with  inner 
portion  destroyed  by  galleries  and  larval  mines.  Fig.  2. — Gal- 
leries in  inner  bark  and  surface  of  wood  of  railroad  ties  and  edg- 
ing strips 16 

VI.  Work  of  the  rock-pine  wood-engraver  (Pityogenes  cariviceps  Lee). 

Galleries  in  inner  bark  and  surface  of  wood 16 

VII.  Scenes  in  the  pine  forests  of  the  Black  Hills  Forest  Reserve — work 
of  Dendroctonus  ponderosa  Hopk.  Fig.  1. — Small  freshly  attacked 
pine  tree,  showing  pitch  tubes.  Fig.  2. — Marks  of  primary  gal- 
leries on  the  surface  of  wood  when  bark  is  removed.  Fig. 
3. — Freshly  attacked  tree,  showing  pitch  tubes;  adjoining  tree 
not  attacked.  Fig.  4. — Dead  tree,  outer  bark  removed  by 
woodpeckers 20 

TEXT  FIGURES. 

Fig.  1.  Work  o*f  the  pine-destroying  beetle  of  the  Black  Hills 9 

2.  Work  of  the  Oregon  Tomicus 10 

3.  Work  of  the  Oregon  Tomicus 11 

4.  Work  of  the  Oregon  Tomicus 12 

5.  Work  of  the  rock-pine  wood-engraver 13 

5 


I 


IXSECT  ENEMIES  OF  THE  PINE  IN  THE  BLACK  HILLS 
FOREST  RESERVE. 


REQUEST,  AUTHORIZATION,  AND  INSTRUCTIONS. 

The  work  herein  reported  wa.s  undertaken  by  request  of  Mr.  Gilford 
Pinehot,  Chief  of  the  Bureau  of  Forestry,  under  authorization  from 
the  honorable  Secretary  of  Agriculture  and  instructions  from  Dr.  L.  O. 
Howard,  Chief  of  the  Division  of  Entomology. 

THE  INVESTIGATING  TRIP. 

The  investigations  were  conducted,  in  company  with  Mr.  Pinehot 
and  his  chief  field  assistant.  Mr.  Griffith,  on  September  1  to  4,  1901, 
along  a  route  traversed  through  the  reserve  from  Spearfish,  via  Iron 
Creek,  Bear  Gulch,  and  Cement  Ridge,  South  Dakota,  Rifle  Pit, 
Wyoming,  and  Spearfish  Creek,  to  Lead,  S.  Dak. 

THE  CONDITIONS  OBSERVED. 

Vast  numbers  of  rock  pine  (Pinus ponderosa  scopvlorum)  that  were 

dying,  or  had  died  within  recent  years,  of  sizes  ranging  in  diameter 
.  from  4  inches  to  the  largest  trees,  were  observed  along  the  route. 
The  dj-ing  trees  occur  in  clumps  of  from  a  few  examples  to  many 
hundreds,  and  in  some  sections,  as  viewed  from  the  summit  of  Cement 
Ridge  and  other  favorable  points,  the  dying,  recently  dead,  and  old 
dead  trees  cover  large  areas. 

THE  AMOUNT  OF  DEAD  TIMBER. 

Mr.  H.  S.  Graves a  estimated  in  1897  that  about  3,000  acres  of  pine 
in  the  Black  Hills  Forest  Reserve  had  been  killed.  Further  data  fur- 
nished by  the  Bureau  of  Forestry  show  that  the  actual  amount  of  dead 
timber,  as  determined  by  Mr.  Griffith  and  party  in  a  detailed  survey  of 
the  timber  resources  of  the  reserve  in  1901,  is,  "'An  average  stand  of 
1,956  feet  board  measure  of  bug-killed  timber  on  116,000  acres,  giving 
a  total  of  226,890,000  feet  board  measure/' 

HISTORICAL  REFERENCES. 

It  is  the  general  opinion  among  settlers  and  others  who  have  had  an 
opportunity  to  note  the  conditions  affecting  the  pine  that  the  dying 
timber  commenced  to  attract  attention  about  six  or  seven  years  ago, 
or  about  1895. 

a Nineteenth  Annual  Report  U.  S.  Geological  Survey,  1897-98,  Part  V,  p.  87. 


8 

The  c\  idence  found  by  the  writer  in  old  dead  standing  and  felled 
trees  indicates  that  the  pine-destroying  beetle  has  been  present,  for  a 
much  longer  time.  It  was  also  evident  that  much  of  the  devastation 
supposed  to  have  been  caused  by  forest  fires  was  caused,  primarily,  by 
insects. 

Mr.  Graves,  in  his  exhaustive  report  on  the  Black  Hills  Forest 
Reserve,"  refers,  on  page  87,  to  insects  and  the  dead  pine  timber  as 
follows: 

On  the  high  limestone  divide,  from  near  Crook  Tower  to  the  head  of  Little  Spear- 
fish  Creek,  there  are  numerous  patches  of  dead  and  dying  timber.  These  patches 
are  usually  rectangular  in  shape  and  follow  the  tops  of  the  divide  and  ridges,  or  run 
lengthwise  up  and  down  the  slope.  This  forest  has  for  the  most  part  not  been  lately 
burned,  and  there  is  a  heavy  matting  of  litter  and  humus  on  the  ground.  The  injury 
is  confined  to  the  limestone  formation  and  to  high  elevations.  The  trees  are  in  many 
cases  second  growth  and  apparently  perfectly  thrifty.  This  injury  is  probably 
caused  by  insects.  On  all  dead  and  dying  trees  examined  were  found  bark  borers,  a 
species  of  the  Scolytidse,  working  under  the  bark.  In  most  cases  the  leaves  were 
clinging  to  trees  which  had  been  dead  for  several  seasons.  While  these  borers  do  not, 
as  a  rule,  attack  vigorous  trees,  no  other  cause  of  the  death  of  this  timber  could  be 
found. 

Mr.  H.  E.  Dewey,  writing  to  the  Division  of  Entomology  from  Lead, 
S.  Dak.,  on  August  12,  1899,  stated: 

*  *  *  There  have  been  none  in  the  trees  this  year  until  last  "Wednesday,  the 
9th.  On  that  day  there  was  a  southwest  wind,  and  a  swarm  of  them  came.  My 
dwelling  is  in  what  was  a  grove  of  young  native  Black  Hills  pines.  The  bugs  settled 
on  the  house  like  a  plague  of  locusts.  At  night  they  left  the  house  and  scattered 
about.  I  have  examined  the  trees,  and  with  one  exception  do  not  find  that  they 
attacked  them.  This  one  excepted  tree  is  a  sight.  Hundreds  of  bugs  settled  on  it 
during  the  night,  and  by  morning  they  had  buried  themselves  out  of  sight  in  the 
trunk.  As  they  bored  their  way  in,  the  dust  from  their  boring,  which  was  very 
fine,  filtered  out  from  the  top  to  the  bottom  of  the  tree  like  fine  sawdust,  and  fell* 
about  the  tree  on  the  ground.  They  could  be  plainly  heard  at  their  work  as  they 
bored  into  the  wood.  The  tree  was  a  vigorous  young  pine  about  15  feet  high  and  6 
inches  in  diameter  at  the  ground,  and  there  is  no  apparent  reason  why  they  should 
select  it  more  than  others.     Last  year  they  were  here  in  June. 

The  following  copy  of  a  letter  addressed  to  the  Department  of  the 
Interior,  Division  of  Forestry,  was  submitted  to  the  author  from  the 
Division  of  Entomology,  with  a  specimen  of  the  insect,  which,  together 
with  the  specimens  sent  with  Mr.  Dewey's  letter,  formed  the  material 
from  which  the  species  was  named  and  descriptive  notes  were  made. 
The  letter  is  dated  Piedmont,  8.  Dak..  August  11,  1898,  and  reads  as 
follows: 

Many  of  the  pine  trees  in  this  vicinity  are  dying.  Small  holes  appear  in  the  bark, 
a  reddish  pitch  exudes,  the  leaves  turn  brown,  and  in  a  few  weeks  the  tree  dies.  I 
think  the  mischief  is  done  by  the  small  black  inseet  inclosed  herewith,  which  I  found 
in  one  of  the  holes.     Is  there  any  remedy? 


Nineteenth  Annual  Reporl  U.  S.  Geological  Survey,  1897-98,  Part  V,  pp.  67-164. 


Bui.  32,  New  Series,  Div.  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  I. 


Work  of  the  Pine-destroying  Beetle  of  the  Black  Hills  <  Dendroctonus 
ponderosa  n.  sp.).  primary  galleries  and  larval  mlnes  in  inner  sur- 
FACE of  living  Bark. 

a.  Entrance  and  basal  chamber;  b,  ventilating  boles  in  roof  of  gallery;  c,  termination. 

The   larval  mines  radiate  from  the  primary  galleries.     About  one-half  natural  size. 
(Original.) 


Bui.  32,  New  Series,  Div.  of  Entomology,  U.  5.  Dept.  of  Agriculture. 


Pla-e:  II. 


Work  of  the  Coarse-writing  Tomicus,  in  inner  Surface  of  Bark  from 

dying  Pine. 

a,  Entrance;  b,  central  chamber;  c,  primary  or  egg  galleries.    Reduced  about  one-half. 

(Original.) 


THE  TROUBLE  CAUSED  BY  INSECTS. 

The  evidence  obtained  from  a  study  of  all  stages  of  the  afflicted  tim- 
ber, including  the  living,  dying,  recently  dead,  and  old  dead  trees,  of 
all  sizes,  and  under  widely  varying  conditions  of  altitude,  exposure, 
geological  formation,  soil,  and  character  of  growth,  indicates  quite 
clearl\r  that  this  widespread,  unhealthy,  dying,  and  dead  condition  of 
the  timber  is  the  work  of  insects. 

THE   PRIMARY   ENEMY. 

The  evidence  found  also  clearly  indicates  that  the  insect  which  makes 
the  first  attack  on  the  living  trees,  and  therefore  the  primary  cause  of 
the  trouble,  is  a  small,  black,  bark-boring  beetle,  belonging  to  a  species 
heretofore  unknown  to  science,  and  appears  to  be  peculiar  to  the  Black 
Hills  region. a 

NAME    OF    THE    BEETLE. 

Since  this  primary  enemy  has  not  been  distinguished  from  a  number 
of  other  bark  beetles  found  in  the  infested  trees,  it  has  not  been  desig- 


FlG.  1.— Work  of  the  pine-destroying  beetle  of  the  Black  Hills,  in  inner  bark  of  dead  tree,    a,  pri- 
mary galleries:  b,  larra mines:  e,  pupre  chambers:  <K  exit  holes.    Reduced  abont  one-half  (original). 

nated  by  a  local  name.     1  would  therefore  suggest  that  hereafter  it  be 
designated  as  "the  pine-destroying  beetle  of  the  Black  Hills,"  and  by 

■  Since  this  was  written  it  has  been  reported  from  Colorado. — A.  D.  H. 


10 


the  technical  or  Latin  name  Dendroctonus  ponderosa.*  The  adult  ia  a 
stout,  dark-brown  to  black  beetle,  individuals  of  which  vary  in  length 
from  -i  to  7  mm.  (about  one-sixth  to  one-fourth  inch).  They  attack 
living  and  healthy  large  and  small  pine  trees,  enter  the  bark  on  the 
main  trunk,  and  each  pair  excavates  a  long,  nearly  straight,  longitudi- 
nal gallery  through  the  inner  bark  (PL  I  and  fig.  1),  usually  grooving 
the  surface  of  the  wood.  Eggs  are  deposited  along  the  sides  of  this 
primary  gallery  und  hatch  into  minute  white  grubs  (larva?),  which 
excavate  mines  through  the  bark  at  right  angles  to  the  primary  gallery 
(tig.  1,  b).     These  mines  are   extended  and   enlarged  as  the  larvae 

increase  in  size,  and  when 
full  grown  each  individual 
excavates  a  broad,  oval 
cavity  in  the  bark  (tig.  1, 
c),  in  which  it  transforms 
to  a  soft,  white  pupa,  and 
then  to  the  adult,  which 
^VV(    II  V)       jf\v^^^         bores  out  through  the  bark 

(/  ^>^^^)  CTS\r^         (fig.  1,  d),  and  flies,  with 

other  adults  of  the  same 
and  other  broods,  in  search 
of  other  living  trees  in 
which  to  excavate  galleries 
and  deposit  eggs  for  an- 
other brood. 

SECONDARY  ENEMIES. 

Many  other  species  of 
bark  beetles  and  other 
bark  and  wood  infesting 
insects  were  found  asso- 
ciated with  the  primary 
enemy  in  the  partly  living 
bark  of  infested  and  dying 
trees,  but  none  of  them  wTere  found  making  an  independent  attack  on 
living  trees.  Therefore  they  must  be  considered  as  secondary  ene- 
mies, which  follow  the  leader  in  the  attack,  and  merely  contribute  to 
the  rapid  and  certain  death  of  the  trees  thus  infested. 

Th>  Oregon  Tomicus  (Tomicus  ovegoni  Eichh.). — This  is  a  small  red- 
dish to  black  bark  beetle,  individuals  of  which  vary  in  length  from 
3.5  mm.  to  4  mm.  It  follows  closely  the  attack  of  the  pine-destroying 
beetle,  and  (Miters  the  bark  on  the  large  and  medium  sized  branches 
and  toward  the  top  of  the  main  stem.     Several  females  excavate  radi- 


Fig.  2.— Work  of  the  Oregon  Tomicus  ( Tomicus  ovegoni  Eichh. ) . 
Primary  galleries  and  larval  mines  in  inner  bark,  a,  En- 
trance; b,  central  chamber  excavated  through  inner  bark; 
c,  egg  galleries;  d,  location  of  central  chamber  not  exca- 
vated through  inner  bark.  Reduced  about  one-half  (origi- 
nal). 


'This  species  lias  heretofore  been  erroneously  identified  as  D.  terebrans  and  D. 
rufipenniSj  and  will  probably  be  found  so  labeled  in  some  collections. 


11 


ating  galleries  from  a  single  entrance  and  a  central  chamber  (fig.  2,  a 
and  b).  The  central  chamber  may  («),  or  may  not  (b),  extend  through 
the  inner  layers  of  bark  and  groove  the  surface  of  the  wood,  but  the 
radiating  galleries  are  nearly  always  grooved  in  the  surface  of  the 
wood,  as  are  also  the  egg  cavities,  which  are  excavated  at  short  inter- 
vals along  the  sides  (figs.  3  and  4).  These  grooved  and  notched  carv- 
ings are  often  very  conspicuous  in  the  surface  of  the  wood  of  trees 
and  logs  for  many  }Tears  after  the  bark  is  removed  or  has  fallen  away. 
The  number  of  galleries  branching  from  the  central  chamber  varies 
from  two  to  five  or 
six,  but  the  normal 
number  is  four — two 
above  and  two  below 
the  entrance.  The 
mode  of  development 
of  the  young  stages  is 
the  same  as  in  the  pre- 
ceding species.  (See 
PL  V.) 

This  is  a  common 
enemy  of  the  rock  pine 
(Pinus  ponder  osa  sco- 
2?ulorum)  throughout 
the  Rocky  Mountain 
region  and  of  P.  pon- 
der osa  west  of  the 
mountains.  It  is  ever 
ready  to  attack  and 
prevent  the  recovery 
of  trees  of  all  sizes 
which  are  suffering 
from  weakened  vital- 
ity. It  is  also  at- 
tracted to  recently 
felled  trees,  and  breeds 
in  enormous  numbers 
in  the  bark  on  the  tops  and  branches.  The  species  was  found  to  be 
exceedingly  common  in  trees  infested  by  the  pine  destroyer  and  on  the 
logs  and  tops  of  those  felled  by  the  lumbermen. 

The  coarse-writing  bark-beetle  (Tomicus  calUgraphus  Germ.  var.  occi- 
<l en  talis). — This  is  much  larger  than  the  Oregon  Tomicus,  but  is  of  the 
same  color  and  general  form.  Individuals  vary  in  length  from  4.5  mm. 
to  6.5  mm.  This  species  also  follows  closely  the  first  attack  by  the 
pine  destrover.     It  enters  the  bark  from  near  the  base  to  toward  the 


Fig.  3.— Work  of  the  Oregon  Tomicus.  Primary  galleries  engraved 
in  surface  of  wood.  Central  chamber  not  extending  into  wood 
except  at  a.    Reduced  about  one-half  (original). 


12 


top  of  the  tree,  and  excavates  three  or  four  long  longitudinal  galleries 
from  a  single  entrance  and  broad  central  chamber  (PI.  II).  The  cen- 
tral chambers  and  galleries  are  usually  grooved  in  the  surface  of  the 
wood,  but  can  be  readily  distinguished  from  those  made  by  the  Oregon 
Tomicus.  It  is  a  common  and  widel}T  distributed  species  over  the 
greater  part  of  the  pine-producing  areas  of  the  United  States  from 
the  Atlantic  coast  to  and  including  the  Rocky  Mountain  region.11  It 
attacks  all  of  the  Eastern  and  Southern  pines,  and  doubtless  several 
of  the  Western  pines  in  addition  to  the  rock  pine,  in  which  it  was 

found  in  large  numbers 
in  the  Black  Hills  region. 
The  wood  -  engra  ding 
Tomicus  (Tomicus  ccela- 
tus  Eichh.). — This  is  a 
much  smaller  and  more 
slender  bark  beetle  than 
the  two  preceding  spe- 
cies. Individuals  vary 
in  length  from  2.6  mm. 
to  3.2  mm.,  and  in  color 
from  dark  red  to  dull 
black.  This  is  also  a 
common,  widely  distrib- 
uted, and  variable  spe- 
cies. It  extends  from 
the  Atlantic  to  the  Pa- 
cific, and  infests  all  of 
the  Eastern  and  South- 
ern pines  and  spruces.  A 
variety  (var.  scopulorurn 
n.  var.)  was  found  in  the 
rock  pine  of  the  Black 
Hills,  and  has  been  col- 
lected by  the  writer  from 
a  number  of  other  spe- 
cies of  Western  pines.  It  attacks  and  breeds  in  the  inner  bark  on  the 
roots,  trunks,  and  branches  of  weakened  and  dying  standing  trees  of 
nil  ages  and  sizes,  from  the  very  young  to  the  oldest  and  largest.  It 
also  breeds  in  immense  numbers  in  the  stumps,  logs,  and  tops  of 
recently  felled  trees. 

Tfieddrk-red  turpentine  beetle  (Dendroctonus  valens  Lee.) — This  is  the 
largest  of  the  known  North  American  bark  beetles.  The  adults  vary 
in  length  from  (>  mm.  to  9.5  mm.     It  attacks  the  bark  on  the  base  of  liv- 


Fig.  4.— Work  of  the  Oregon  Tomicus.  Primary  galleries  en- 
graved in  surface  of  wood.  Central  chamber  extending  into 
wood.    Reduced  about  one-half  (original). 


"The  Western  form  seems  to  be  sufficiently  different  in  some  minor  characters  to 
warrant   {\\\<  distinction  in  variety  name — occidental^. 


Bui.  32,  New  Series,  Div.  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  III. 


j't^iifct  T^" 

jJ?<M    %Y> 

j^y^ ?  .::ir.--.^r-  ,^fC^| 

^TP^Gte*  . 

,     e-.'.;v  :.■■■-;•?     •    ! 

"  »       ~=^ij 

.    V^jt^lS^i 

iJirr^tTS 

'f#5^fTV 

-^5 

-•^Sffiyyl* 

Pl--^^,^;^^ 

^^^^^^fe^^^3£Sr 

Bui.  32,  New  Series,  Div.  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  IV. 


13 


ing  and  dying  standing  trees  and  the  stumps  of  felled  ones,  and  exca- 
vates a  broad,  crooked,  longitudinal  gallery.  The  eggs  are  deposited 
in  masses  along  one  side,  and  when  they  hatch  the  Larvae  work  together 
and  excavate  a  broad  chamber,  instead  of  making  individual  larval  bur- 
rows, as  is  the  rule  with  most  other  species.  One  of  the  striking  pecul- 
iarities of  this  insect  is  the  habit  of  the  adult  and  larva  of  living  in 
the  quantity  of  semiliquid  pitch  or  turpentine  which  accumulates  in 
the  primary  gallery  and  brood  chamber.  While  this  beetle  is  capable 
of  attacking  and  developing  its  broods  in  the  bark  of  a  living,  healthy 
tree,  it  seldom  causes  the  death  of  trees  unaided  by  other  insects.  It 
does,  however,  contribute  to 
the  death  of  trees  attacked  by 
the  pine-destroying  and  other 
destructive  beetles.  It  is  a 
common  insect  in  the  Rocky 
Mountain  region  and  west  to 
the  Cascades.  A  variety  (Den- 
droctonus  valens  orientalis)  is 
common  in  the  East,  attacking 
in  the  same  manner  all  of  the 
Eastern  pines. 

The  Western  pine  llylur- 
gqps  (Hylurgops  subcostulatus 
Mann.). — This  is  a  common, 
dull  brown  to  black  bark  beetle, 
ranging  in  length  from  3. 5  mm. 
to  4.5  mm.,  which  attacks  and 
breeds  in  the  bark  on  the  roots 
and  bases  of  dying  trees  and  the 
stumps  and  logs  of  felled  ones. 
It  excavates  a  single  longitudi- 
nal gallery,  and  the  broods  de- 
velop in  confused  or  irregular 
larval  mines  in  the  inner  bark, 
but  rarely  groove  the  surface 
of  the  wood.  This  is  one  of 
the  commonest  bark  beetles 
from  the  Rocky  Mountain  region  to  the  Pacific  coast,  and  will  evi- 
dently be  found  wherever  the  rock  pine  or  Western  yellow  pine  grows. 

The  pine-root  bark-beetle  (Sylastes  jporosm  Lee). — This  is  a  black, 
elongate,  slender  bark  beetle,  varying  in  length  from  I  mm.  to  5  mm. 
It  attacks  the  bark  on  the  roots  of  the  Western  pine  and  excavates  a 
single  longitudinal  gallery  from  which  the  brood  burrows  radiate, 
and  the  broods  develop  in  the  usual  manner.  It  was  found  in  the 
bark  on  the  roots  of  young  seedling  pines  which  had  recently  died, 


Fig.  5.— Work  of  the  rock  pine  wood  engraver  I  Pi- 
tyogenes    cariniceps   Lee).     Primary   galleries   and 

larval  mines  in  inner  bark  and  surface  of  wood. 
Reduced  about  one  half  (original). 


14 

and  also  in  the  bark  on  the  roots  of  the  stump  of  a  recently  felled 
tree  in  the  Black  Hills.  This  is  also  a  common  species  of  the  Rock}- 
Mountain  pine  regions. 

Branch  and  twig  beetles. — The  large  and  small  branches  and  termi- 
nal twigs  of  the  trees  that  were  dying  from  the  attack  of  the  pine- 
destroying  beetle  were  found  to  be  infested  by  a  number  of  described 
and  undescribed  species  of  the  genus  Pityophthorus  and  by  Pityogenes 
cariniceps,  all  of  which  attack  the  bark  as  soon  as  the  trees  commence 
to  die,  and  contribute,  more  or  less,  to  hastening  the  death  of  the  trees. 

Ambrosia  or  timber  beetles  and  viood-boring  grubs. — The  wood  of  the 
trees  was  found  to  be  infested  by  the  Western  hemlock  wood  stainer 
( Gnathotrichus  snlcatus  Lee),  the  Western  pine  wood  stainer  ( Gnatho- 
trichus occidentalis  Hopk.  MS.),  and  several  unidentified  Buprestid 
and  Cerambycid  larvae,  which  attack  the  trees,  and  when  they  com- 
mence to  die  bore  into  the  sapwood  and  contribute  to  its  rapid  decay 
by  giving  entrance  through  their  burrows  to  wood-decaying  fungi. 

SMALL  TREES  DYING  FROM  OTHER  CAUSES. 

The  rock-pine  pitch  worm. — In  addition  to  the  trees  killed  by  the 
pine-destroying  beetle,  quite  a  number  of  young  pines  2  and  3  inches 
in  diameter  were  found  in  the  vicinity  of  Spearfish  and  Crow  Peak 
that  were  seriously  injured  b}T  the  larva  of  an  undetermined  Sesiid 
moth  working  in  the  living  bark  of  the  main  stem  and  causing  ugly 
wounds.  Successive  attacks  on  the  same  tree  weaken  its  vitality  and 
attract  the  Oregon  Tomicus  and  species  of  Pyogenes  and  Pityophtho- 
rus, which  infest  the  main  stem  and  branches,  while  a  number  of  the 
root-infesting  bark  beetles  and  a  pine  weevil  attack  the  base  and  roots, 
and  the  tree  soon  dies.  Onty  a  dead  and  dry  larva  and  a  dead  chrysa- 
lis of  this  insect  were  found.  The  characters  exhibited  by  these  speci- 
mens do  not  agree  with  the  descriptions  of  the  larva  of  the  sequoia 
and  pine-destroying  Sesiid  (Bembecia  sequoia—  Vespamima  sequoia?  Hy. 
Edw.a)  or  of  the  larva  and  chrysalis  of  the  pine  Sesiid  (Ilarmonia 
pini= Parharmonia  pini  Kellicott b). 

The  destructive  habits  of  this  class  of  enemies  of  trees  (which 
includes  the  common  peach-tree  borer)  suggest  that  this  may  be  a 
common  and  destructive  enemy  of  u  reproduction "  pines  in  the  Black 
Hills  and  other  pine-producing  areas  of  the  West. 

Thepi?ie  weevil. — In  another  section  near  the  Wyoming  and  South 
Dakota  lines  man}^  young  trees  were  observed  which  were  apparently 
dying  from  the  attack  of  a  pine  weevil  (Pissodes  sp.),  or  the  combined 
attacks  of  this  insect,  a  root  fungus  disease,  and  a  number  of  species 
of  bark  beetles. 

Mem.  Am.  Mus.  Nat.  Hist.,  vol.  1,  part  vi,  Mongr.  Sesiidse.  Am.  North  of  Mex. 
1901,  p.  263,  with  bib.  ref. 
"Ibid.,  p.  264. 


15 

INSECT  ENEMIES  OF  THE  FOLIAGE. 

Little  time  was  had  to  collect  or  study  the  enemies  of  the  foliage, 
but  from  general  observations  there  was  no  perceptible  injury  from 
this  class  of  depredators. 

NATURAL    ENEMIES    OF   THE  DESTRUCTIVE  AND  INJURIOUS 

INSECTS. 

Numerous  species  of  predaceous  and  parasitic  insects  were  found 
associated  with  the  primary  and  secondary  enemies.  Some  evidence 
was  found  of  the  beneficial  work  of  birds,  and  a  few  examples  of  the 
pine-destroying  beetle  were  found  that  had  been  killed  by  a  disease, 
but  in  no  case  was  there  sufficient  evidence  to  indicate  that  any  of 
these  natural  enemies,  or  all  combined,  were  in  sufficient  numbers  to 
render  any  special  service  toward  bringing  the  trouble  to  an  end. 
They  were  undoubtedly  rendering  some  service,  however,  in  prevent- 
ing the  rapid  multiplication  of  the  pine  destroyer,  which  would  other- 
wise occur. 

PREDACEOUS   ENEMIES. 

The  bluish-green  predaceous  beetle  {Trogosita  virescens  Fab.). — This  is 
an  elongate,  flattened,  shining,  green  beetle,  varying  in  length  from 
10  mm.  to  13  mm.,  and  in  width  from  3  mm.  to  1  mm.  The  larva 
is  a  long,  slender,  reddish  to  whitish  worm,  with  shining  black  head 
and  prothoracic  plates.  This  recognized  predatory  enemy  of  bark- 
infesting  insects  was  frequently  found  associated  with  colonies  of  the 
pine-destroying  beetle  and  the  secondary  enemies,  and  a  few  adults 
were  found  hiding  beneath  the  flakes  of  outer  bark.  This  widely  dis- 
tributed insect  in  North  America  has  not  been  sufficiently  studied  to 
determine  its  true  relation  to  the  destructive  enemies  of  the  trees,  but 
it  is  evidently  quite  beneticial. 

Clerid  beetles  and  th^eir  larvce. — The  slender,  reddish  larvae  of  unde- 
termined species  of  this  class  of  predaceous  enemies  of  bark  beetles 
were  found  in  small  numbers  in  the  bark  with  the  broods  of  the 
destructive  and  other  species  of  bark  beetles.  This  class  of  beneticial 
insects  usually  renders  great  service  in  reducing  the  numbers  of  the 
destructive  and  injurious  species.  Therefore  their  scarcity  in  this 
region  may  have  had  much  to  do  with  the  rapid  multiplication  and 
spread  of  the  pine-destroying  Dendroctonus.  While  collecting  speci- 
mens of  bark  beetles  from  saw  logs  in  a  mill  yard  at  Boulder,  Colo., 
on  August  25.  one  of  these  Clerids  ((  'A  rus  nigrivt  ntris  Lee.)  was  very 
common.  The  active,  ant-like  adults,  which  are  black,  marked  with 
transverse  patches  of  gray,  vary  in  length  from  6  mm.  to  8  mm.,  and  in 
width  from  2.5  mm.  to  3  mm.  The  larva  is  a  slender,  pale  red  worm. 
The  adult  feeds  on  and  destroys  erreat  numbers  of  the  adult  bark 


16 

beetles  before  they  enter  the  bark  and  when  they  emerge,  while  the 
larva  destroys  the  larva  and  broods  in  the  bark. 

A  red-hug  enemy  ofhark-heetles. — A  .small,  red  to  brown  Hemipter- 
ous  bug  of  the  family  Acanthiidae  and  subfamily  Anthocorina  was 
found  in  all  stages  of  development,  associated  writh  colonies  of  the  pine- 
destroying  beetle  and  its  allies,  in  the  bark  of  recently  attacked  living 
and  dying  trees.  These  little  relatives  of  the  bedbug  and  the  flower 
bugs  are  recognized  as  aggressive  enemies  of  bark  beetles,  both  in  the 
East  and  West.  The  one  found  in  the  Black  Hills  is  evidently  Pizos- 
tethus  califomicus  Reut.  The  adult  is  about  3  mm.  long,  slender, 
grayish,  and  exceedingly  active.  The  young  forms  are  usually  bright 
red,  active  little  creatures  which  attack  and  suck  out  the  liquids  from 
the  bark  beetles  and  their  larva?.  The  adult  bug  also  attacks  and 
kills  the  adult  bark  beetles.  While  this  is  a  common  and  active  enemy 
of  the  smaller  bark  beetle,  it  probably  does  not  render  much  service 
toward  checking  the  ravages  of  the  destructive  species. 

Other  predaceoas  beetles. — There  are  also  a  number  of  predaceous 
beetles  of  the  families  Colydiidre,  Tenebrionidae,  Histeridae,  and 
Staphylinidas  which  were  found  in  greater  or  less  numbers  in  the 
bark  of  infested  trees,  but  their  exact  relation  to  the  destructive 
beetle  was  not  determined. 

PARASITIC   INSECTS. 

Several  parasites  belonging  to  the  order  Hymenoptera  and  families 
Braconidae,  Chalcididae,  and  Proctotrupidae  were  found  to  be  enemies  of 
the  smaller  bark  beetle  larva?  and  adults,  but  none  were  found  attack- 
ing the  pine-destroying  species.  Therefore  there  does  not  seem  to  be 
much  service  rendered  by  this  class  of  insects,  which  are  usually  so 
efficient  in  reducing  the  numbers  of  bark  beetles. 

PARASITIC   FUNGI. 

A  few  examples  of  the  adults  and  larvae  of  the  pine-destroying  beetle 
were  found  which  had  evidently  been  killed  by  a  fungus  disease,  but 
this  was  by  no  means  common  enough  to  have  rendered  any  service 
in  checking  its  ravages. 

BIRDS   AS   ENEMIES   OF   THE    DESTRUCTIVE   BEETLE. 

A  few  old  dead  trees  and  some  which  had  been  recently  infested 
which  showed  evidence  of  the  beneficial  work  of  woodpeckers  were 
observed  in  some  localities,  but  hundreds  of  other  insect-killed  trees 
showed  no  trace  of  work  by  the  birds.  Therefore  there  appears  to  be 
very  little  service  rendered  from  this  source.  This  is  evidently  due 
to  a  scarcity  of  the  birds  and  to  the  fact  that  the  habit  of  the  insect 
transforming  to  the  adult  in  the  inner  bark  makes  it  less  accessible  to 
the  birds  than  are  the  spruce-destroying  beetle  and  other  bark  beetles 
which  undergo  this  change  in  the  outer  bark. 


Bui.  32,  New  Series,  Div    of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  V. 


Bui.  32,  New  Series,  Div.  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  VI. 


Work  of  the  Rock  Pine-wood  Engraver  <  Pityogenes  cariniceps  Lecj.  Galleries 
in  inner  Bark  and  Surface  of  Wood.  About  one-third  Natural  Size.  (Origi- 
nal.) 


Bui.  32,  New  Series,  Div.  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  VI. 


Work  of  the  Rock  Pine-wood  Engraver  i  Pityogenes  cariniceps  Lec.  Galleries 
in  inner  Bark  and  Surface  of  Wood.  About  one-third  Natural  Size.  (.Origi- 
nal.) 


17 

HOW  THE  TREES  ARE  ATTACKED  AND  KILLED. 

Many  hundreds  of  trees  were  examined  during  the  investigation, 
including*  those  that  were  living  and  perfectly  healthy,  living  and 
freshly  attacked,  infested  and  dying,  recently  dead,  and  old  dead  ones 
which  bore  evidence  of  having  been  killed  by  the  pine-destroying 
beetle.  All  stages  of  the  insect,  including  the  adult,  the  eggy  different 
stages  of  the  larva,  the  pupa,  and  recently  transformed  beetles,  were 
observed  and  studied,  as  were  also  all  stages  of  the  primary  entrance, 
the  gallery  and  brood  mines  in  the  living,  dying,  and  dead  bark,  and 
also  the  primary  gallery  grooves  on  the  surface  of  the  wood  of  old 
dead  trees  and  logs  from  which  the  bark  had  fallen  and  decayed. 

The  evidences  gathered  from  these  studies,  and  from  information 
conve}Ted  in  Mr.  Dewey's  letter,  quoted  on  another  page,  indicate  that 
the  principal  attack  is  made  in  August,  when  it  would  seem  the  beetles 
migrate  in  swarms  from  the  dying  trees  and  settle  on  the  living  ones, 
which  they  attack  and  infest  in  large  numbers  from  near  the  base  to 
the  upper  part  of  the  main  trunk  or  stem. 

The  trees  that  are  attacked  by  a  sufficient  number  of  the  beetles  to 
overcome  the  resistance  exerted  by  the  vital  forces  of  the  plant  com- 
mence to  decline,  and  by  winter  or  the  following  spring  they  die  and 
the  leaves  turn  yellow  and  red.  Those  not  attacked  by  sufficient  num- 
bers of  the  beetles  to  overcome  this  vital  resistance  recover  and  are 
usually  exempt  from  future  attacks;  the  wounds  heal  and  are  covered 
over  by  subsequent  layers  of  wood,  thus  causing  pitch  spots  or  gum- 
streak  defects  in  the  wood. 

The  details  of  the  work  of  the  attacking  force  of  beetles  on  a  living 
tree  ma}7  be  briefly  described  as  follows : 

Both  sexes  settle  on  their  victim,  usuall}^  in  large  numbers,  and  the 
males  (?)a  commence  to  excavate  the  entrance  burrows,  which  are  usu- 
ally hidden  in  a  crevice  or  beneath  a  flake  of  the  outer  bark.  The 
reddish,  sawdust-like  borings  thus  produced  and  thrown  out  fall  to  the 
ground  around  the  base  and  lodge  in  the  loose  outer  bark  on  the  trunk. 
When  they  enter  the  inner  living  bark,  or  bast,  the  tree  commences 
to  exert  its  resistance  b}^  throwing  out  pitch  to  till  and  heal  the  fresh 
wounds  in  the  living  tissue.  Then  the  struggle  between  the  resisting 
force  of  the  plant  and  the  beetles  begins  in  earnest.  Each  female 
joins  her  mate,  and  together  they  continue  the  excavation.  The  bor- 
ings and  pitch  are  disposed  of  by  being  pushed  out  and  formed  into 
a  pitch  tube  at  the  mouth  of  the  entrance  burrow  (PL  VII,  tigs.  1,  3, 
and  4).  The  inner  bark  is  entered  obliquely  and  subtransversely  to 
the  cambium  and  surface  of  the  wood,  where  a  broadened  cavity  is 
excavated  for  the  accommodation  and  temporary  occupation  of  the 

a  While  it  was  not  positively  determined  that  the  male  of  this  species  excavates 
the  first  entrance,  it  is  the  habit  of  many  other  bark  beetles,  and  is  probably  followed 
by  this. 

16274— No.  32—02 2 


18 

pair,  probably  until  the  principal  flow  of  pitch  is  exhausted.  The 
gallery  is  then  extended  (probably  by  the  female)  transversely  or  sub- 
transversely  for  a  short  distance  (seldom  more  than  an  inch),  and  then 
longitudinally  up  or  down  the  tree,  but  usually  up,  varying  from  a 
few  inches  to  a  foot  and  a  half,  the  normal  length  being  about  1  foot. 
As.  soon  as  the  gallery  has  been  extended  1  or  2  inches  from  the 
entrance  and  basal  cavity,  small  notches,  or  cavities,  are  excavated  in 
the  sides  of  the  gallery,  in  each  of  which  an  egg  is  deposited,  and  so 
on  until  the  gallery  is  completed.  As  the  eggs  are  deposited,  the  bor- 
ings, instead  of  being  thrown  out  at  the  entrance,  are  closely  packed 
in  the  entrance  burrow,  basal  cavity,  and  gallerv,  except  near  the 
farther  end,  which  is  kept  open,  enlarged,  or  extended  to  one  side  or 
the  other,  as  it  is  occupied  b}T  the  parent  beetles,  after  their  work  of 
constructing  the  egg  gallery  is  completed,  until  they  die  (PL  I). 

The  bark  of  an  infested  tree  is  usually  occupied  by  one  of  these 
primary  galleries  in  every  1  to  6  inches  of  circumference  from  near  the 
base  to  near  the  middle  of  the  trunk  (PL  VII,  tig.  2).  Therefore  they 
effectually  check  the  normal  movements  of  the  sap,  and  the  larval 
mines,  which  radiate  from  the  primary  gallery,  destroy  the  intervening 
bark  and  complete  the  girdling  process. 

Ten  or  twenty,  or  even  forty  or  fifty  pairs  of  beetles,  attacking  a 
tree  6  or  8  inches  in  diameter,  would  have  little  or  no  effect  or*  its 
vitalit}7  if  scattered  over  the  trunk  from  the  base  to  near  the  top,  but 
if  concentrated  on  a  limited  space  on  the  upper  part  of  the  trunk,  and 
distributed  so  that  there  is  a  gallery  at  intervals  of  about  every 
inch  of  the  circumference,  fort}^  or  fift}T  galleries  are  sufficient  to  so 
seriously  affect  the  tree  that  other  insects  are  attracted  to  it,  and  it 
soon  dies  from  the  girdling  effect  of  the  primary  galleries  and  brood 
mines.  The  marks  of  as  man}7  as  seven  galleries  were  observed  in  a 
single  chip,  6  inches  wide  and  12-J-  inches  long  (PL  III,  fig.  2),  cut  from 
a  tree  that  had  been  killed  b}T  the  beetles.  This,  with  many  other 
observations  relating  to  the  number  of  pitch  tubes  on  freshly  attacked 
trees  and  the  galleries  in  the  bark  of  dead  and  dying  ones,  indicates 
that  the  average  tree  killed  by  the  beetles  has  from  one  hundred  to 
two  hundred  galleries  in  30  to  40  square  feet  of  bark  from  the  middle 
to  base  of  the  main  stem  or  trunk.  The  number  of  eggs  deposited 
in  each  gallery  depends  on  the  number  of  galleries  within  a  given 
area  of  bark  and  the  success  of  the  attack.  They  vary  from  one  or 
two  to  about  one  hundred,  but  the  normal  number  appears  to  be  about 
forty  to  fifty.  If  only  one-half  of  these  develop  to  adults  there  are 
four  thousand  or  five  thousand  beetles  to  emerge  from  a  single  tree  8 
to  10  inches  in  diameter.  Therefore  the  number  of  beetles  that  maj7 
emerge  from  the  thousands  of  trees  that  die  in  a  single  year  would 
make  a  swarm  of  millions  of  individuals.  Even  if  this  number  were 
reduced  one-half,  it  will  be  readily  seen  how  the  trouble  may  be 
rapidly  extended  over  vast  areas  of  forests. 


19 

CHARACTERISTIC  FEATURES  OF  THE  LIVING,  DYING,  AND  DEAD 
TREES  INFESTED  AND  KILLED  BY  THE  BEETLE. 

The  characteristic  features  which  are  of  importance  to  the  forester 
and  lumberman  in  identifying  the  presence  and  the  work  of  the  pine- 
destroying  beetle  are  as  follows: 

BORINGS   AND   PITCH   TUBES. 

The  first  indication  of  attack  is  the  red  dust  or  borings  lodged  in  the 
loose  bark  and  fallen  around  the  base  of  the  tree.  The  next  and  more 
conspicuous  evidence  is  the  presence  of  numerous  small  masses  of  pitch 
or  so-called  pitch  tubes  on  the  outer  bark  at  the  mouth  of  the  entrance 
burrows.  (PL  VII. ,  figs.  1,  3,  4.)  If  the  pitch  is  fresh  and  mixed 
with  reddish  and  white  borings,  it  indicates  a  recent  attack  and  the 
presence  of  the  living  beetles  in  the  bark.  If,  however,  the  pitch  is 
dry  and  hardened,  without  traces  of  fresh  borings  or  the  presence  of 
living  beetles,  and  the  tree  is  living,  it  indicates  an  abandoned  attack 
and  that  the  tree  will  recover. 

APPEARANCE    OF    THE    LEAVES. 

The  leaves  of  trees  dying  from  attack  by  the  beetle  present  first  a 
pale-yellow  appearance  in  the  tops  and  tips  of  the  branches,  followed 
by  a  general  yellowing  of  all  the  leaves,  thus  presenting  from  a  long 
distance  a  marked  contrast  to  the  dark,  healthy  green  of  the  surround- 
ing living  foliage.  If  the  bark  is  stripped  off  and  examined  when  the 
trees  are  in  this  condition,  all  stages  from  eggs  to  fully-developed 
broods  will  usually  be  found,  together  with  numerous  other  secondary 
enemies  of  the  trees  and  enemies  of  the  insects.  The  leaves  do  not 
fall  from  the  twigs  for  possibly  two  or  three  years  after  the  trees 
die  and  the  broods  of  beetles  emerge,  but  they  soon  change  from  yel- 
low to  red.  and  thus  become  even  more  conspicuous.  The  normal 
length  of  time  the  leaves  remain  on  the  twigs  has  not  been  determined, 
but  the  greater  number  evidently  fall  during  the  second  or  third  year, 
leaving  the  twigs  almost  bare,  with  the  exception  of  a  few  leaves  on  the 
tips  which  may  adhere  for  a  much  longer  time. 

APPEARANCE  OF  THE  TREES  THAT  HAVE  BEEN  DEAD  THREE  YEARS  OR 

MORE. 

Little  opportunity  was  had  to  obtain  information  on  the  character- 
istic appearance  at  different  stages  of  deterioration,  but  it  would  appear 
from  such  observations  and  general  comparisons  as  could  be  made  that 
the  twigs  and  some  of  the  branches  commence  to  fall  within  three  or 
four  years,  and  that  after  the  fourth  year  rapid  decay  sets  in,  and  the 
tops  commence  to  break  off. 


20 

EVIDENCE  OF  THE  WORK  OF  THE  BEETLE  ON  OLD  DEAD  TREES. 

After  the  trees  have  been  dead  many  years  most  of  them  decay  at 
the  ba.se  and  fall,  while  the  main  trunks  or  snags  of  others  remain 
standing;  yet  as  long  as  the  surface  of  the  wood  remains  sound  the 
characteristic  longitudinal  gallery  grooves  will  be  more  or  less  distinct, 
and  serve  to  indicate  that  the  trees  were  attacked  while  living.  Pieces 
of  the  old  bark  will  also  usually  show  traces  of  the  galleries  and  indi- 
cate by  the  pitch-preserved  tissue  that  the  galleries  were  excavated  in 
living  bark.  Traces  of  the  pitch  tubes  ma}T  also  remain  on  the  outer 
bark  for  many  }Tears  and  serve  to  indicate  the  cause  of  the  trouble. 

RELATION  OF  WOOD-BORING   INSECTS  AND  WOOD-DESTROYING 
FUNGI  TO  THE  RAPID  DETERIORATION  OF  THE  WOOD. 

As  previously  indicated,  there  are  a  number  of  wood-boring  insects 
which  bore  into  the  sapwood  of  dying  and  dead  trees.  Some  also 
penetrate  the  heartwood.  Some  of  these  wood-infesting  insects  enter 
tne  wood  as  soon  as  the  tree  commences  to  die,  others  after  it  is  dead, 
and  still  others  at  different  stages  of  the  decline  and  decay  as  long  as 
there  is  an}^thing  left  for  them  to  work  in.  It  is  only  those,  however, 
that  enter  the  wood  while  it  is  }^et  of  value  for  commercial  purposes 
that  need  to  be  specially  mentioned  in  this  connection.  Next  to  the 
one  that  makes  the  primaiy  attack,  those  borers  which  enter  the  sound 
wood  are  probably  of  the  greatest  importance.  They  not  only  cause 
pin-hole  and  wormhole  defects,  which  depreciate  the  value  of  the  lum- 
ber and  other  products  into  which  the  wood  of  the  dying  and  dead 
trees  may  be  converted,  but  they  give  entrance  to  wood-decaying  fungi, 
causing  rapid  decay  of  the  wood  of  the  standing  trees  which  would 
otherwise  remain  sound  for  a  much  longer  period. 

While  the  injuries  by  these  wood-boring  insects  are  by  no  means  as 
common  where  there  are  a  great  many  dead  and  dying  trees  as  where 
there  are  only  a  few,  it  was  found  to  be  sufficient  in  some  sections  to 
cause,  in  connection  with  the  wood-decaying  fungi,  a  worthless  condi- 
tion of  the  timber  over  large  areas.  Indeed,  it  would  seem  from  such 
observations  as  we  were  able  to  make  that  unless  the  trees  are  cut 
and  converted  into  lumber,  ties,  cordwood,  or  other  commercial  prod- 
ucts within  two  or  three  years  after  they  commence  to  die,  very  little 
of  value  is  left. 

SUGGESTIONS  FOR  PREVENTING  LOSSES. 

The  limited  time  devoted  to  the  study  of  this  new  insect  was  not 
sufficient  to  determine  the  details  in  its  life  histoiy  and  habits  which 
are  usually  so  necessary  in  the  consideration  of  remedies,  but  some 
genera]  features  were  noted,  which,  in  connection  with  the  information 
acquired  from  special  investigations  of  the  closely  related  destructive 


Bui.  32,  New  Series,  Div.  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  VII. 


1. — Small  freshly  attacked  Pine  Tree,   showing 
Pitch  Tubes. 


Fi3.  2. — Marks  of  primary  Galleries  on 
the    Surface   of  Wood  when    Bark  is 

REMOVED. 


i 

'"i  f*£ l  ? 

!    . 

(I 

Fig.  3. — Freshly  attacked  Tree,  showing  Pitch  Tubes. 
Adjoining  Tree  not  attacked. 


Fig.  4. — Dead  Tree  ;  outer  Bark  removed 
by  Woodpeckers. 


Scenes  in  the  Pine  Forests  of  the  Black  Hills  Forest  Reserve. 


-  21 

pine-bark  beetle a  of  the  middle  Appalachian  region  and  the  spruce- 
destroying  beetle  b  of  the  Northeast,  will  warrant,  it  is  believed,  some 
suggestions  for  the  prevention  of  losses. 

METHODS   OF   COMBATING   THE    ENEMY   AND    PREVENTING    LOSSES    FROM 

ITS   RAVAGES. 

When  a  trouble  has  been  going  on  six  or  seven  years  and  lias 
reached  the  magnitude  of  the  one  under  consideration,  it  is  very  plain 
that  unless  some  natural  agencies  appear  to  either  modify  or  check  it, 
its  control  is  beyond  all  human  effort.  On  the  other  hand,  if  there 
are  beneficial  influences  at  work  which  are  reducing  the  numbers  of 
the  insect  and  checking  its  destructive  ravages,  there  is  much  that  can 
b  1one  toward  aiding  nature  in  the  suppression  and  subjugation  of 
an  unruly  species.  The  evidences  found  indicate  that  the  latter  is  true 
in  regard  to  this  trouble.  While  many  freshly  attacked  living  trees 
and  thickly  infested  dying  ones  were  observed  in  different  sections  of 
the  reserve,  showing  that  great  numbers  of  the  beetles  are  at  work 
and  continuing  the  trouble,  it  was  plain  that  the  force  of  the  attack 
has  from  some  cause  been  materially  weakened. 

TO    REDUCE   THE    NUMBERS. 

It  appears  that  the  pine-destroying  beetle  of  the  Black  Hills,  like 
its  Eastern  relatives,  depends  on  the  trees  killed  by  it  for  the  aug- 
mentation of  its  numbers  and  the  perpetuation  of  its  power  of  killing 
more  trees.  Therefore  it  is  only  necessary  that  the  attacking  force  be 
further  reduced  to  a  point  where  it  can  no  longer  overcome  the  vital 
resistance  of  the  trees  on  which  it  concentrates  its  attack,  in  order  to 
successfully  defeat  it  and  secure  its  extermination. 

The  fact  that  the  attacking  force  of  the  enemy  is  already  weakened 
from  natural  agencies  suggests  that  they  can  be  reduced  by  artificial 
means  below  their  power  of  killing  more  trees  next  season,  and  thus 
bring  the  trouble  to  an  end.  Therefore  the  following  are  suggested 
and  recommended  as  probably  the  best  methods  of  accomplishing  this 
result: 

(1)  Determine  the  location  and  extent  of  areas  in  which  trees  were 
attacked  during  the  summer  and  fall  of  1901  and  the  number  of  trees 
now  infested  with  living  broods  of  the  pine-destroying  beetle. 

(2)  Select  those  areas  in  which  there  are  the  largest  number  of 
infested  trees  and  mark  the  same  for  cutting. 

(3)  Secure,  by  sale  contracts  or  otherwise,  the  cutting  of  these  trees 
and  the  removal  of  the  bark  from  the  infested  parts  of  the  main  trunks 
and  stumps  prior  to  the  1st  of  May,  1902.     The  drying  of  the  removed 

a  Dendroctonus  frontalis  (Zimm.)  var.  destructor  Hopk.,  Bui.  56,  W.  Va.  Agric.  Exp. 
Station,  1899. 

b Dendroctonus piceaperda  Hopk.,  Bui.  28  n.  s.,  Div.  Ent.,  U.  S.  Dept.  Agric,  1901. 


22 

infested  bark  and  surface  of  the  wood  will  effectually  destroy  the 
insects.  In  addition,  the  logs  so  treated  will  be  protected  next  spring 
and  summer  from  the  attack  of  wood-boring  insects,  and  thus  be 
almost  or  quite  as  valuable  for  all  commercial  purposes  as  if  cut 
from  living  trees. 

It  is  not  necessary  that  all  infested  trees  in  the  reserve  or  those  of  all 
other  infested  areas  should  be  thus  cut  and  barked,  but  it  is  important 
that  a  large  per  cent  should  be  so  treated  in  order  to  insure  a  sufficient 
reduction  of  the  beetles  to  check  their  destructive  ravages. 

SUGGESTIONS  FOR  PREVENTING  FURTHER  TROUBLE. 

It  is  believed  that  the  prevention  of  further  trouble  may  be  effected 
by  means  of  girdled  and  otherwise  treated  trap  trees,  but  the  best 
method  of  treating  the  trees  and  the  proper  time  or  periods  to  do  the 
work  remain  to  be  determined. 

No  experiments  of  this  kind  have  been  conducted  with  the  rock  pine, 
and  it  is  not  positively  known  when  the  beetles  commence  to  fly  or  what 
is  the  period  of  their  greatest  abundance  or  swarms.  Therefore  it  is 
suggested  that  a  special  line  of  experiments  be  conducted,  between  the 
1st  of  May  and  the  1st  of  September,  to  determine  the  best  methods 
of  providing  trap  trees  and  the  best  time  to  do  the  work  to  secure  the 
desired  end,  viz,  that  of  attracting  the  migrating  beetles  to  certain 
trees  or  sections  of  the  forest,  where  they  can  be  subsequently 
destroyed  by  cutting  the  trees  and  removing  the  bark. 

TO    PREVENT    LOSSES    FROM    WOOD-BORING    INSECTS   AND    WOOD-DESTROYING    FUNGI. 

The  evidence  found  relating  to  the  work  of  wood- boring  insects  and 
wood-destroying  fungi,  which  cooperate  in  effecting  a  rapid  deteriora- 
tion of  the  trees  killed  b}^  beetles,  suggests  that  all  trees  should  be  cut 
within  three  or  four  years  after  they  commence  to  die,  the  sooner  the 
better,  and  be  worked  up  into  lumber,  ties,  mine  timbers,  and  cord 
wood,  in  order  to  prevent  the  great  loss  of  valuable  products  which 
would  otherwise  follow.  Such -material,  if  in  excess  of  the  demand 
for  immediate  consumption,  might  be  stored  where  it  would  keep  dry 
and  be  protected  from  tire.  It  would  thus  remain  sound  for  many 
years  and  serve  to  supply  the  demand  for  material  which  would 
otherwise  have  to  be  drawn  from  the  living  timber. 

THE  PROTECTION  OF  LIVING  TIMBER. 

Since  it  is  of  the  greatest  importance  that  the  living  timber  in  the 
reserve  should  be  protected  and  preserved  for  the  heav}T  demands 
upon  its  resources  which,  owing  to  the  vast  mining,  commercial,  and 
other  interests,  it  will  be  required  to  meet,  the  prevention  of  unneces- 
sary cutting  on  account  of  injuries,  or  alleged  injuries,  from  insects 
should  receive  special  attention. 


23 

EVIDENCES  OF  UNNECESSARY  CUTTING  OF  LIVING  TIMBER. 

One  of  the  special  objects  of  the  investigation  was  to  determine 
whether  or  not  unnecessary  cutting  of  living  timber  had  been  done  by 
certain  contractors  who  had  purchased,  at  a  reduced  price,  the  speci- 
fied'4  bug-infested"  and  "bug-killed"  timber.  Therefore,  upon  the 
request  of  Mr.  Pinchot,  the  writer  made  a  careful  study  of  the  con- 
ditions found  in  an  extensive  cutting  in  a  "draw"  east  of  Dead  Ox 
Canyon  of  Big  Spearhsh  Creek. 

Much  conclusive  evidence  was  found  that  a  large  per  cent  of  the  trees 
cut  here  and  worked  into  railroad  ties  had  been  living  and  uninjured 
by  insects  when  felled.     The  evidence  may  be  briefly  stated  as  follows: 

All  trees  that  are  attacked  and  injured  by  the  pine  destroying  beetle, 
whether  in  small  or  large  numbers,  plainly  show  the  characteristic  work 
of  the  beetles  in  the  bark  and  on  the  surface  of  the  wood,  as  previously 
described  (p.  17)  and  illustrated  (PI.  Ill,  %.  2;  Pis.  IV.  VII).  The 
character  of  the  work  will  also  indicate  whether  or  not  a  given  tree 
was  living,  dying,  or  dead  when  felled  and  the  bark  removed.  The 
operation  of  scoring,  hewing,  and  barking  the  ties  in  this  particular 
cutting  had  evidently  followed  closely  the  felling  of  the  trees.  There- 
fore the  inner  portion  of  the  bark  and  outer  or  adjoining  portion  of 
the  wood  of  the  scoring  chips  and  the  barked  surface  of  the  ties  from 
"bug-infested"  and  "bug-killed"  trees  bore  abundant  evidence  of  the 
work  of  the  insect  and  the  condition  of  the  tree  when  felled,  while 
those  from  healthy  living  trees,  not  injured  or  infested  by  bark-boring 
insects,  showed  no  traces  whatever  of  the  work  of  the  beetle  or  of  any 
other  "bug"  or  insect. 

The  records  of  ties,  counted  as  observed  in  the  woods  and  examined 
for  the  work  of  insects,  show  that  out  of  207  ties  onlv  55  bore  evidence 
of  having  been  cut  from  "bug-infested"  and  "bug-killed"  trees, 
while  the  other  152  bore  no  evidence  of  insect  work  on  the  barked 
surface,  but  showed  from  the  condition  of  this  surface  that  they  had 
been  cut  from  healthy,  living  trees;  also  that  some  of  the  trees  had  been 
cut  in  the  winter  when  the  sap  was  down  and  that  others  had  been  cut 
in  the  spring  when  the  sap  was  up  and  the  bark  would  peel.  There- 
fore it  would  appear  that  a  large  amount  of  living  timber  had  been 
cut  which  it  was  plainly  evident  the  Government  desired  should  remain 
standing. 

SUGGESTIONS  CONCERNING  TIMBER-CUTTING  CONTRACTS. 

In  order  to  provide  or  guard  against  the  cutting  of  living,  uninfested 
trees,  along  with  the  seriously  injured  and  dying  ones,  it  might  be 
suggested  that  it  be  plainly  stated  in  contracts  and  instructions  that  no 
living  tree  shall  be  cut  which  does  not  show,  in  the  inner  bark  next  to 
the  wood,  the  presence  of  large  numbers  of  living  insects,  of  the  species 
known  as  the  pine-destroying  beetle,  or  any  other  insect  or  insects 
which  may  hereafter  be  designated  as  destructive  enemies  of  the  trees. 


2± 
NEED  OF  FURTHER  INVESTIGATION. 

While  considerable  evidence  was  found  during  the  time  devoted  to 
the  investigation,  there  yet  remains  much  to  be  determined  by  detailed 
study  and  experiments  relating  to  the  peculiar  conditions  which  bring 
about  the  invasion  of  a  rare  or  new  insect  and  the  conditions  which  con- 
tribute to  its  rapid  multiplication  and  destructive  work,  as  well  as  those 
which  contribute  to  its  decline  and  sudden  disappearance.  There  are 
also  many  facts,  yet  to  be  determined,  relating  to  the  life  history  and 
peculiar  habits  of  the  pine-destroying  beetle  and  other  numerous 
enemies  of  the  trees,  and  the  natural  enemies  of  such  insects.  The 
determination  of  these  facts  is  very  necessary  in  order  to  suggest  the 
best  methods  of  preventing  losses  in  the  future.  It  will  also  help  us 
to  utilize  nature's  methods  of  protecting  such  of  the  species  as  are  of 
use  to  man  and  destroying  those  that  are  objectionable. 

Cutting  and  harking  the  infested  trees  this  winter  would  be  an  exper- 
iment of  great  importance,  not  only  in  its  prospects  of  ending  the 
trouble,  but  in  demonstrating  whether  or  not  it  is  a  practicable  method 
to  be  adopted  under  similar  conditions  in  the  future.  It  will  also  be 
of  interest,  and  probabty  of  considerable  economic  importance,  to  note 
the  effect  that  this  process  of  insect  destruction  will  have  on  the  other 
injurious  and  beneficial  insects  involved. 

The  exjyeriments  of  girdling,  cutting,  and  treating  trees  with  a  view 
of  rendering  them  attractive  to  the  migrating  beetles,  and  thus  pro- 
viding traps  for  them,  is  a  line  of  work  which  should  receive  special 
attention  next  summer.  It  would  serve  to  demonstrate,  or  at  least 
indicate,  several  things  which  it  is  quite  necessary  to  know  in  order 
to  adopt  successful  methods  of  preventing  future  trouble  from  insect 
ravages  on  the  pines  of  this  reserve.  It  would  demonstrate  whether 
or  not  the  beetles  that  emerge  from  the  infested  trees  which  have  not 
been  cut  and  barked  could  be  attracted  to  trap  trees;  how  and  when 
the  rock  pine  can  be  girdled  or  treated  to  exert  the  greatest  attraction 
to  the  principal  enemies,  and  how  the  insects  thus  trapped  can  be 
best  destroyed.  It  would  also  contribute  greatly  to  the  study  of  the 
life  history  and  habits  of  the  primary  and  secondary  enemies  of  the 
trees  and  the  enemies  of  the  insects. 

There  are  other  features  relating  to  the  kinds  of  insects  and  fungi 
that  attack  trees  girdled  b}^  different  methods,  or  girdled  and  felled  at 
different  times  of  the  }^ear,  which  should  be  determined.  Indeed, 
there  are  many  and  varied  subjects  relating  to  the  insects  of  the  rock 
pine  which  should  be  studied  during  the  progress  of  the  present 
trouble,  in  order  to  accumulate  data  that  will  be  of  service  in  prevent- 
ing and  checking  future  destructive  invasions  in  the  pine  forests  of  the 
Rocky  Mountain  region. 


UNIVERSITY  OF  FLORIDA 


3  1262  09216  4861 

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